Clive, 2nd ed. User's manual. Section 2 
SYNOPSYS

import "clive/zx/fscmp"

func Diff(fs1, fs2 zx.Getter, path ...string) <-chan zx.Chg
func Diffs(fs1, fs2 zx.Getter, path ...string) ([]zx.Chg, error)

DESCRIPTION

Compare two file systems. For testing mostly and not using find. Refer to
zx/repl for a better way using find.

FUNCTIONS

func Diff(fs1, fs2 zx.Getter, path ...string) <-chan zx.Chg
    Compute changes for fs1 to become like fs2 and send them through the
    returned chan. If no path is given, "/" is used.

func Diffs(fs1, fs2 zx.Getter, path ...string) ([]zx.Chg, error)
    Like Diff, but return a slice of changes (mostly for testing)

User's manual, 2nd ed. Section 2